1. Field of the Invention
The present invention relates, in general terms, to diaphragm clutch mechanisms, especially for motor vehicles, of the kind comprising a substantially annular cover, at least one pressure plate intended to be fixed to the cover in rotation whilst being movable relative thereto, a substantially annular diaphragm comprising a peripheral part forming a Belleville washer for acting on the pressure plate, and a central part fragmented into radial fingers for engagement by a clutch release bearing, and assembly means pivotally securing the diaphragm to the cover by continously urging said diaphragm axially, under an elastic clamping load, against a primary abutment located on the cover, said assembly means comprising, on the one hand, retaining members which are coupled to the cover and which have an axial part passing through the diaphragm via passages formed between the radial fingers of the diaphragm and an end wing bent with the aid of a notch in the axial part thereof and defining together with the said axial part a wedging elbow, and, on the other hand, a ring wedged in the said wedging elbow and designed to provide a secondary abutment for the diaphragm which is disposed substantially opposite the primary abutment.
Such a clutch mechanism is intended to be attached by means of its cover to a reaction plate, integral with a first shaft, (usually a drive shaft) with the interposition between the reaction plate and the pressure plate of a friction disc fixed in rotation to a second shaft, (usually a driven shaft). Arranged around the driven shaft is a clutch release bearing, operable to act on the radial fingers of the diaphragm to disengage the clutch from its normally engaged condition in which the pressure plate clamps the friction disc against the reaction plate under the action of the Belleville washer bearing on the primary abutment.
2. Description of the Related Art
Such a clutch mechanism is described in French patent application No. 76/05,485 of Feb. 27, 1976, for which there is at least in part a corresponding U.S. Pat. No. 4,084,674, and comprises, on the one hand, relatively thin and flat retaining members and, on the other hand, a ring which is centered on the axial part of the said retaining members via the edge of its inner periphery having a substantially flat radial orientation portion in contact with the wedging elbow. Furthermore, the said ring has, on its outer periphery, a part in the form of a wide-open V for forming the secondary abutment and for stiffening the said ring. Thus, this ring has a twisted shape with, in cross-section, a radial portion, an inclined portion and another portion inclined in the opposite direction to the preceding one.
Such a device has been and still is satisfactory.
Nevertheless, the advantage of this device is that it has a ring of relatively high rigidity and that, to keep the diaphragm constantly applied against the primary abutment, it exerts on the said ring a considerable prestress which increases the hysteresis effect of the diaphragm even more when it tilts between the primary and secondary abutments, and causes wide load variations in proportion to the unavoidable operational wear of the diaphragm and the abutments between which it is tiltably mounted.
To overcome these disadvantages, it is possible to replace this ring by a thinner spring-steel ring, as described in German patent application No. 2,843,317 of Oct. 4th 1978, but such a solution is expensive and the ring is not located in its entirety radially beyond the axial part of the retaining members, thus making assembly more complicated.